diff --git a/guetzli-recursively.py b/guetzli-recursively.py
index c196582..fde4c7c 100644
--- a/guetzli-recursively.py
+++ b/guetzli-recursively.py
@@ -1,43 +1,43 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 from os import path, walk, remove, rename
+from imghdr import what
 from subprocess import call
 from sys import argv
 top_dir = argv[1]
 TEMP_FILE = 'temp.jpg'
-extensions = ('jpeg', 'jpg')
+TYPES = ('jpeg',)
 
 for dirpath, dirnames, files in walk(top_dir):
     for name in files:
-        for extension in extensions:
-            if name.lower().endswith(extension):
-                # Get urls
-                url = path.join(dirpath, name)
-                print(url)
-                url_out = path.join(top_dir, TEMP_FILE)
-                # Remove temp image
+        if what(path.join(dirpath, name)) in TYPES:
+            # Get urls
+            url = path.join(dirpath, name)
+            print(url)
+            url_out = path.join(top_dir, TEMP_FILE)
+            # Remove temp image
+            try:
+                remove(url_out)
+            except:
+                pass
+            # Execute guetzli
+            call(['guetzli', url, url_out])
+            # Print your have saved
+            size_source = path.getsize(url)
+            try:
+                size_out = path.getsize(url_out)
+            except:
+                size_out = size_source
+            size_acurate = 100 * size_out / size_source
+            # Check if it is cost effective to replace it
+            if size_acurate < 100:
+                # Remove source
                 try:
-                    remove(url_out)
+                    remove(url)
                 except:
                     pass
-                # Execute guetzli
-                call(['guetzli', url, url_out])
-                # Print your have saved
-                size_source = path.getsize(url)
-                try:
-                    size_out = path.getsize(url_out)
-                except:
-                    size_out = size_source
-                size_acurate = 100 * size_out / size_source
-                # Check if it is cost effective to replace it
-                if size_acurate < 100:
-                    # Remove source
-                    try:
-                        remove(url)
-                    except:
-                        pass
-                    # Move temp to source
-                    rename(url_out, url)
-                    print('Save ' + str(round(100 - size_acurate, 2)) + '%')
-                else:
-                    print('It is not necessary to optimize')
+                # Move temp to source
+                rename(url_out, url)
+                print('Save ' + str(round(100 - size_acurate, 2)) + '%')
+            else:
+                print('It is not necessary to optimize')